Apparatus for recovery of silver from spent photographic solutions



J. N. MEGESI APPARATUS FOR RECOVERY OF SILVER FROM SPENT PHOTOGRAPHIC SOLUTIONS Filed Jan. 12, 1960 July 10, 1962 3,043,432

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Josavn N. Mcczsi HTTORNEYS United States Patent 3,043,432 APPARATUS FUR RECOVERY OF SILVER FROM SPENT PHQTGGRAPHIC SOLUTIONS Joseph N. Megesi, Cleveland, ()hio, assignor to Fairco Reclaiming Service, Fairview Park, Ohio, a corporation of Ohio Filed Jan. 12, 1960, Ser. No. 2,012 4 Claims. (Cl. 210-99) This invention relates, as indicated, to an improved apparatus for the recovery of silver from solutions, particularly spent photographic solutions; for example, fix and stop solutions. More particularly, this invention is concerned with an improved apparatus of the type adapted to continuous operation in modern photographic print and film processing and/or developing shops utilizing automatic or manual replenishing devices to maintain strength of chemical solutions within feasible range.

In my Patent No. 2,905,323, dated September 22, 1959, I have described and claimed an apparatus useful in the recovery of silver from photographic solutions. The

present invention represents an improvement on the ap paratus shown, described and claimed in the aforesaid patent.

The silver salts, e.g., silver bromide, used in the manufacture of photographic paper and film when fixed by sodium thiosulphate or other commercial prepared fixatives or stop agents produces a complex silver salt which is soluble in the solution. In those procedures utilizing constant replenishment of stock solution so as to maintain a standard concentration for satisfactory fixation of photographic paper and film, the used solutions are allowed to flow into an overflow pipe of the tanks involved into the waste drain. In the larger processing shops, considerable quantities of silver are thus lost.

It is a principal object of the present invention to provide an apparatus for the recovery of silver values which are otherwise lost.

In my prior Patent 2,905,323, I describe and claim a apparatus comprising a vessel divided into three superimposed sections, lower, central and upper. The central section was separated from the other by perforated dividers, and the free space between such dividers was substantially filled with a fluid permeable free metal containing medium, the metal being above silver in the electromotive series. An inlet duct was provided communi eating with the lower section, an outlet duct leading from the upper section, and a pipe communicating with the upper and lower sections only was internally disposed in the apparatus. The pipe was provided with a discharge outlet at its upper end positioned at a level which was above the level'of the outlet duct leading from the upper chamber or section. The purpose of the pipe in that apparatus and in the present apparatus is to provide for fluid to flow through the apparatus even though the normal path of the fluid up through the perforated plate should become blocked by the accumulation of sediment and metal within the fluid permeable metal-containing medium disposed in the central section. The unobstructed path provided by the pipe serves as a safety relief and overflow device. In order that the fluid should follow the preferential path through the metal containing fluid permeable medium, the discharge outlet in the relief pipe is located at a point above the level of the outlet duct in the wall of the apparatus.

The foregoing device necessitated operation against the relatively high hydrostatic head of fluid contained within the vessel, and frequently in commercial installations auxiliary pumping means were needed to force the fluid through the apparatus.

By virtue of the improvements comprising the present invention, I am able to utilize a hydrostatic head to aid 3,043,432 Patented July 10, 1962 ice in forcing the fluid through the apparatus without the necessary employment of auxiliary pumping means.

The improvement of the present invention will be better understood by reference to the annexed drawing where- FIG. 1 is a side elevational view of one embodiment of my improved apparatus.

FIG. 2 is a cross-sectional view taken on the line 22 of FIG. 4.

FIG. 3 is a top view of the apparatus shown in FIG. 1.

FIG. 4 is a cross-sectional view taken on the line 44 in FIG. 3.

Briefly stated, my invention is in the provision in the apparatus described in Patent No. 2,905,323, of the inlet means for introducing spent photographic solution into the upper end of the pipe which communicates with the upper and lower section only. Thus, my invention is in an apparatus for the recovery of silver values from spent photographic solutions containing silver in solution comprising a vessel divided into three superimposed sections, lower, central and upper, the central section being separated from the others by perforated dividers and having the free space therebetween substantially filled with a fluid permeable free metal-containing medium, said metal being above silver in the electromotive series. An outlet duct is provided leading from the upper section. A safety or relief pipe is provided internally communicating with the lower and upper. sections only. This pipe is provided with a discharge outlet at a level above the level of the outlet duct and is adapted to permit the free flow of fluid out of the pipe when the fluid permeable medium becomes clogged. Cover means removably secured to the upper open end of the vessel are also provided. Inlet means are provided according to this invention for introducing spent photographic solution into the upper end of said pipe.

Referring more particularly to the drawings, there is provided a vessel 1 which is conveniently of cylindrical form, divided into three cylindrical sections by perforated plates 2 and 3. The lower section 4 between the bottom 5 of the vessel 1 and the first perforated plate 2 communicates with the upper section'9 by means of the pipe 16 having'suitable inlet port or ports 17 in its lower end. The pipe 16 may run the entire length of the tank. At the upper end, the pipe 16 isprovided with a suitable port or ports 18. The upper chamber 9 is provided with an outlet duct 11 located at a level in the upper chamber 9 which is below the level of the outlet port 18 in the pipe 16.

The central section 7 is bounded by the two perforated plates 2 and 3 and the walls of the vessel 1. This section is filled with a suitable fluid permeable material 8 comprising a free metal which is above silver in the electromotive series.

The upper section 9 is bounded by the perforated plate 3, a suitable cover 10 and the walls of the vessel 1.

The cover 10may be secured to the top section 9 by any suitable means such as bolts 12 hinged at 13 on the wall of the container and fitting into slots 14 in the cover.

Appropriate plates 2 and 3 are conveniently supported by lugs 15 affixed to the inner wall of the vessel 1. Any suitable means of locating the perforated plate may be employed and it is desirable that both plates be removable in the event replacement should become necessary.

Instead of inlet means being provided to the lower section 4 as shown in Patent 2,905,323, inlet to the improved apparatus of spent photographic solution is through the cover 10 and into the pipe @16, at the upper end thereof. The point of exit of the fluid into the pipe 16 is preferably below the discharge outlet "18 in the pipe 16. One means of accomplishing this is shown in FIG. 4 where there is provided a nipple l9 piercing the cover 10. The nipple 19 is conveniently supported in the cover 10 by means of the flange 20. The tubular portion of the nipple 19 (21) extends through the cover 10 and into the pipe 16 terminating at its lower extremity at a point below the level of the discharge outlet of the pipe 16. The crosssectional area of the nipple 19 is less than the cross-sectional area of the pipe 16 so that in the event of clogging of the central section 7, fluid may flow through the tubular portion 21 of the nipple 19, and with a slight reverse upon itself flow out of the discharge outlet 18 in the pipe 16 through the annular space between the concentrically disposed tubes. Although circular parts have been shown as the pipe 16 and the nipple 19, it is clear that parts of any cross-sectional configuration may be employed so long as the two parts bear a cross-sectional relationship to each other as indicated above.

The materials of construction are generally those which will not react to a substantial degree with the silver containing fluid. Accordingly the vessel and the perforated plates 2 and 3 are conveniently constructed of stainless steel as is the overflow pipe 16. Obviously other materials of construction can be used such as plastics, e.g. urea-formaldehyde resins (Bakelite) representative of the thermoset type of material, and polyethylene representative of the thermoplastic type of material. Except for the property of non-reactivity with the solutions being processed, any suitable material of construction can be used.

The fluid permeable medium contained within the central section 7 must be a flee metal which is above silver in the electromotive series. For most practical purposes, this includes iron in the form of steel wool, iron turnings, iron wire, screening or chips of iron, and copper in the form of copper wool, turnings, wire, screen or chips. Other metals such as tin, zinc, aluminum, cadmium, etc. may be used, but experience will show that economical operation is achieved with steel wool and/or copper wool. The fluid permeable medium may be a mixture of iron with copper or any of the other metals above silver in the electromotive series with or without added inert material. Most usually, the apparatus is satisfactorily operated when a mixture of No. 3, 4 and 5 grades steel wools is intermingled with copper screening. Instead of loose metal wool, turnings, wire, screening, etc. a powdered metal of much higher surface area and hence much greater chemical activity may be dispersed on a suitable medium such as aluminum or other porous inert substance. In another modification, the Wire screen may be carried in a removable cartridge. Such a cartridge is convenient where the silver recovery is done at a point remote from the film processing laboratory.

The principle of operation of this device is the same as the device described and claimed in my Patent No. 2,905,323 and depends upon the property of metals above silver in the electromotive series to go into solution and replace silver from such solution. Thus, the complex silver salts formed during print and/ or film processing on passing over iron and/ or copper yield the silver in form of metal deposited upon the iron and/ or copper. The silver is replaced by an equivalent amount of iron and/ or copper which goes into solution in place of the silver. When the iron and copper has been completely coated with silver it is a relatively easy matter to recover the silver metal from the wool screen matrix.

In operation, spent silver-containing photographic solution is introduced into the inlet 16, (as by direct pipe connection or through a funnel, forming no part of this invention and hence not shown) by-passing the discharge port 18. The fluid is introduced to the lower chamber 4 through the ports 17 at the lower end of pipe 16. The hydrostatic head in the pipe 16 forces the fluid up through the holes 23 in the perforated plate 2 into contact with the metal wool 8. As explained above, the wool extracts the silver from solution causing a build up of such metal in the central section '7. After a period of time, the central section will become filled indicating readiness for physical recovery of the metal.

Under this condition, feeding of solution into the unit must cease unless suitable relief means are provided. In accordance with the present case, the fluid flow at the ports 17 will cease, and the incoming fluid be forced up into the annulus between the tubular portion 21 and the tube or pipe 16 and out through the discharge port 18. From this point the fluid Will leave the apparatus via the outlet 11 and be delivered to the waste disposal system.

A specific embodiment of this invention contemplates a tank of type 316 stainless steel 38 inches high and 9 inches in diameter. The retaim'ng plates 2 and 3 are stainless steel plates 8 and inches in diameter with a central hole 22 of 7 inch for the clogging relief tube 16. Holes 23 of approximately 0.75 inch diameter are punched in the retaining plate to allow the silver containing solution to pass upwardly to the outlet 11 in the upper section 7. The retaining plates are placed on suit able quarter inch lugs '15 welded to the interior wall of the tank 4 inches from the base and spaced apart. A set of lugs 15 for the upper plate is provided 4 inches from the top of the tank spaced 90 apart. The outlet 11 is a 0.75 inch opening threaded for stainless steel pipe and located 3% inches from the top of the tank. The non-clogging safety relief tube is conveniently made of plastic, hard rubber, non-metal or stainless steel tubing 37.5 inches long and 0.5 inch in diameter, inch ID. The tube is conveniently perforated in the region of the lower section 4 with quarter inch diameter holes spaced about 2.5 inches apart throughout the area of the approximately 4 inches from the base of the tube. The top of the safety relief tube 16 is notched out 0.5 inch to allow the solution to flow out of the tube in case of clogging. The inlet nipple conveniently has an 0.1). of .25 inch and the tubular portion is conveniently inch long. The nipple may be welded to the cover it or loosely positioned therein for convenient removal.

The cover is conveniently a stainless steel flanged plate fitted with a rubber gasket to seal the tank and prevent the escape of any gases which may form in the chemical reaction. The cover is conveniently held in place by reinforced metal straps fastened to the tank body by four wing bolts.

There has thus been provided an improvement over my prior apparatus in respect of the means of introducing the silver containing solution enabling advantage to be taken of hydrostatic head in pipe 16 to aid in forcing fluid through the silver recovery medium.

Other modes of applying the principle of this invention may be employed instead of those specifically set forth above, changes being made as regards the details herein disclosed, provided the elements set forth in any of the following claims or the equivalent of such may be employed.

It is, therefore, particularly pointed out and distinctly claimed as the invention:

1. In an apparatus for the recovery of silver values from spent photographic solutions containing silver in solution having a vessel divided into three superimposed sections, lower, central, and upper, the central section being separated from the others by perforated dividers and having the free space therebetween substantially filled with a fluid permeable free metal containing medium, said metal being above silver in the electromotive sries, an outlet duct leading from the upper section, a pipe communicating with the lower and upper sections only, said pipe extending into said upper section having an unimpeded discharge outlet at a level above the level of said outlet duct whereby to permit free flow of fluid out of said pipe when the fluid permeable medium becomes clogged, and a cover removably secured to the upper open end of said vessel, the improvement which comprises inlet means for introducing spent photographic solution into the upper end of said pipe at a level within said pipe, intermediate the level of said discharge outlet and the level of said outlet duct.

2. In an apparatus for the recovery of silver values from spent photographic solutions containing silver in solution having a vessel divided into three superimposed sections, lower, central, and upper, the central section being separated from the others by perforated dividers and having the free space therebetween substantially filled with a fluid permeable free metal containing medium, said metal being above silver in the electromotive series, an outlet duct leading from the upper section, a pipe communicating with the lower and upper sections only, said pipe extending into said upper section having an unimpeded discharge outlet at a level above the level of said outlet duct whereby to permit free flow of fluid out of said pipe when the fluid permeable medium becomes clogged, and a cover removably secured to the upper open end of said vessel, the improvement which comprises inlet means piercing the cover for introducing spent photographic solution into the upper end of said pipe at a point below said discharge outlet in said pipe and above the level of said outlet duct.

3. In an apparatus for the recovery of silver values from spent photographicsolutions containing silver in solution having a vessel divided into three superimposed sections, lower, central, and upper, the central section being separated from the others by perforated dividers and having the free space therebetween substantially filled with a fluid permeable free metal containing medium, said metal being above silver in the electromotive series, an outlet duct leading from the upper section, a pipe communicating with the lower and upper sections only, said pipe extending into said upper section having an unimpeded discharge outlet at a level above the level of said outlet duct whereby to permit free flow of fluid out of said pipe when the fluid permeable medium becomes clogged, and a cover removably secured to the upper open end of said vessel, the improvement which comprises inlet means piercing the cover including a nipple having a cross-sectional area less than the cross-sectional area of said pipe and extending into said pipe on an axis substantially common-with that of said pipe at a level within said pipe, intermediate the level of said discharge outlet and the level of said outlet duct.

4. In an apparatus for the recovery of silver values from spent photographic solutions containing silver in solution having a vessel divided into three superimposed sections, lower, central, and upper, the central section being separated from the others by perforated dividers and having the free space therebetween substantially filled with a fluid permeable free metal containing medium, said metal being above silver in the electromotive series, an outlet duct leading from the upper section, a pipe communicating with the lower and upper sections only, said pipe extending into said upper section having an unimpeded discharge outlet at a level above the level of said outlet duct whereby to permit free flow of fluid out of said pipe when the fluid permeable medium becomes clogged, and a cover removably secured to the upper open end of said vessel, the improvement which comprises inlet means piercing the cover including a nipple having a flange at its upper end shouldered against said cover, a tubular portion having an external cross-sectional area less than the internal cross-sectional area of said pipe, the lower extremity of said tubular portion being disposed at a point below said discharge outlet in said pipe and above the level of said outlet duct.

References Cited in the file of this patent UNITED STATES PATENTS 2,007,615 Ross July 9, 1935 2,017,615 Brown Oct. 15, 1935 2,076,934 Burckhalter Apr. 13, 1937 2,137,397 Haldeman Nov. 22, 1938 2,211,305 Werder Aug. 13, 1940 2,348,651 Schelly May 9, 1944 2,905,323 Megesi V Sept. 22, 1959 

4. IN AN APPARATUS FOR THE RECOVERY OF SILVER VALUES FROM SPENT PHOTOGRAPHIC SOLUTIONS CONTAINING SILVER IN SOLUTION HAVING A VESSEL DIVIDED INTO THREE SUPERIMPOSED SECTIONS, LOWER, CENTRAL, AND UPPER, THE CENTRAL SECTION BEING SEPARATED FROM THE OTHERS BY PERFORATED DIVIDERS AND HAVING THE FREE SPACE THEREBETWEEN SUBSTANTIALLY FILLED WITH A FLUID PERMEABLE FREE METAL CONTAINING MEDIUM,SAID METAL BEING ABOVE SILVER IN THE ELECTROMOTIVE SERIES, AN OUTLET DUCT LEADING FROM THE UPPER SECTION, A PIPE COMMUNICATING WITH THE LOWER AND UPPER SECTIONS ONLY, SAID PIPE EXTENDING INTO SAID UPPER SECTION HAVING AN UNIMPEDED DUSCHARGE OUTLET AT A LEVEL ABOVE THE LEVEL OF SAID OUTLET DUCT WHEREBY TO PERMIT FREE FLOW OF FLUID OUT OF SAID PIPE WHEN THE FLUID PERMEABLE MEDIUM BECOMES CLOGGED, AND A COVER REMOVABLY SECURED TO THE UPPER OPEN END OF SAID VESSEL, THE IMPROVEMENT WHICH COMPRISES INLET MEANS PIERCING THE COVER INCLUDING A NIPPLE HAVING A FLANGE AT ITS UPPER END SHOULDERED AGAINST SAID COVER, A TUBULAR PORTION HAVING AN EXTERNAL CROSS-SECTIONAL AREA LESS THAN THE INTERNAL CROSS-SECTIONAL AREA OF SAID PIPE, THE LOWER EXTREMITY OF SAID TUBULAR PORTION BEING DISPOSED AT A POINT BELOW SAID DISCHARGE OUTLET IN SAID PIPE AND ABOVE THE LEVEL OF SAID OUTLET DUCT. 